Effects of B2S3 additive on diamond crystallization at HPHT conditions

Abstract

Diamond possesses extremely excellent properties, which make it a potentially transformative material in an extensive range of applications. Herein, diamonds were synthesized in a FeNiCo–C system with B₂S₃ as an additive by a temperature-gradient growth method at high temperature and high pressure (HPHT) conditions. The effects of the B₂S₃ additive in the FeNiCo–C system on diamond crystallization were characterized using Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. FTIR result shows the presence of positive-charged N⁺ in the diamond crystal synthesized with the B₂S₃ additive, and its concentration was estimated to be around 30 ppm. Moreover, the XPS measurements confirm that N⁺ can combine with boron to form a B–N bond. Furthermore, the Hall effect result indicates that the resistivity of the diamond crystal synthesized with B₂S₃ was reduced to 3.89 × 10 Ω cm, whereas, the resistivity of the diamond synthesized with the same weight of B₂S₃ additive along with Ti/Cu as the nitrogen removal agent dropped sharply to 2.51 × 10⁻¹ Ω cm.